Direct 2D spatial coherence determination using the Fourier analysis method Multi parameter characterization of the P04 beamline at PETRA III

We present a systematic 2D spatial-coherence analysis of the soft-X-ray beamline P04 at PETRA III for various beamline configurations. The influence of two different beam-defining apertures on the spatial coherence properties of the beam is discussed and optimal conditions for coherence-based experiments are found. A significant degradation of the spatial coherence in the vertical direction has been measured and sources of this degradation are identified and discussed. The Fourier-analysis method, which gives fast and simple access to the 2D spatial coherence function of the X-ray beam, is used for the experiment. Here, we exploit the charge scattering of a disordered nanodot sample allowing the use of arbitrary X-ray photon energies with this method

Time course of ouabain and furosemide effects on transepithelial potential differnce in cortical thick ascending limgbs of rabbit nephrons

Publisher Summary: This chapter discusses the mechanism of NaCl transport in the cortical thick ascending limb of Henle's loop. It describes that NaCl transport in this nephron segment produces a lumen positive electrical transepithelial potential difference (PD). This PD is eliminated by substituting large anions for chloride, by ouabain added to bath and by diuretics like furosemide added to the luminal perfusate. An improved method to record transepithelial electrical resistance (RT) in conjunction with PD measurements at both ends of the isolated perfused cTAL segment has made it possible to investigate passive parameters, that is, the cation selectivity of the paracellular shunt pathway, and aspects of the active transport mechanism. Furosemide and ouabain experiments with high time resolution are performed to obtain some insight into the sidedness and mechanism of the inhibitor action. The chapter presents a model that is proposed for NaCl transport in cTAL in which a basolateral ATP dependent Na+-K+ transport is the primary event. The lumen positive PD drives a large fraction of the Na+ through the preferably sodium permeable paracellular shunt

Electrophysiological investigation of microdissected gastric glands of bullfrog I. Basolateral membrane properties in the resting state

In the present experiments we have made a new attempt to characterize the ion transport properties of H+-secreting cells of the gastric mucosa using electrophysiological techniques. Individual gastric glands of bullfrog fundus mucosa were manually dissected, mounted in holding pipettes and superfused with various test solutions while individual cells were punctured with conventional or H+-sensitive double-barrelled microelectrodes. All measurements were performed in the resting state (0.1 mmol/l cimetidine). In HCO3− containing control Ringer solution the cell membrane potential (Vb) averaged −45.6±0.9 mV (±SEM, n=54). From the fast initial Vb responses to changing bath K+, Na+, Cl− or HCO3− concentrations we deduced that the basolateral cell membrane contains conductances for K+, Na+, and Cl− but not for HCO3−, and that a Na+-HCO3− cotransporter is not present. The K+ conductance was inhibited by Ba2+ (3 mmol/l), but the Cl− conductance was not inhibited by 4,4′ diisothiocyanato-stilbene-2,2′disulphonic acid (DIDS, 0.3 mmol/l), nor selectively inhibited by 5-nitro-2-(3)-phenylpropyl-aminobenzoate (NPPB, 10 (μmol/l). In a great number of cells the Vb response to Cl− substitution revealed two components: an initial spiking depolarization which reflected conductive Cl− efflux and a secondary slow hyperpolarization, the origin of which was not immediately evident. Since the latter response could be mimicked by CO2-free perfusion, strongly depressed by Ba2+ and eliminated by DIDS, we conclude that it reflects HCO3− uptake into the cells via a DIDS sensitive Cl−/HCO3− exchanger which alkalinizes the cells and stimulates the basolateral K+ conductance. Our results confirm, revise and extend the results of previous, less direct, investigations of gastric cell ion transport

Electrophysiological investigation of microdissected gastric glands of bullfrog II. Basolateral membrane properties in the presence of histamine

Following the technical approach described in the preceding publication we have investigated if, and how, stimulation of gastric HCl secretion affects the basolateral ion transport properties of oxyntopeptic cells of Rana catesbeiana stomach. To this end microdissected gastric glands were punctured with conventional or H+-sensitive glass microelectrodes and the effects of changing bath ion concentrations on the cell membrane potential (Vb) and cell pH (pHi) were determined. Except for a transient alkalinization, histamine (0.5 mmol/l) did not significantly affect Vb or pHi. The latter averaged 7.18±0.03 (mean±SEM, n=5) under resting conditions (0.1 mmol/l cimetidine) and 7.21±0.07 (n=5) in the presence of histamine. In addition, neither the initial velocity nor the final steady-state value of the cell alkalinization following a 10∶1 reduction of bath Cl− concentration changed in the presence of histamine, and the same holds true for the cell acidification following a 10∶1 reduction of bath HCO3− concentration. These observations indicate that the basolateral Cl−/HCO3− exchanger was not stimulated by histamine, and that no other base transporters were activated. By contrast, the Vb response to elevation of bath K+ concentration decreased, and so did the initial depolarizing Vb response to bath Cl− substitution, while the secondary hyperpolarizing response increased. The latter observations are compatible with the notion that stimulation by histamine reduced a pH-insensitive part of the basolateral K+ conductance and reduced also the basolateral Cl− conductance